Search

The thermal performance of the high-power flip-chip light-emitting diodes (FC LEDs) is analyzed by using a quantitative parametric analysis of the thermal dependence on the chip contact area, bump configuration and bump defects. The optimized LED FC bump configuration design and good bonding quality in the chip bonding process are crucial for improving the thermal performance and extending the operating longevity of high-power FC LEDs.

The synthesis and photophysical properties of the axially substituted complexes 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium chloride, 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium bromide and 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium iodide are described. The different axial ligands have shown negligible effect on the linear absorption, emission and transient difference absorption spectra, but the heavier axial ligands have affected significantly the excited-state lifetime, triplet excited-state quantum yield and efficiency to generate singlet oxygen.

A passively mode-locked Nd:YLF laser with an output-coupling LT-[In.sub.0.25][Ga.sub.0.75]As absorber grown by metal-organic chemical-vapor deposition technique is demonstrated. The continuous-wave mode-locking average output power of 530 mW is obtained at the incident pump power of 10 W corresponding to the peak power of 1.8 kW and pulse energy of 5.4 nJ.

A simple lattice model with T-shaped molecules in two dimensions is introduced that exhibits a rich range of morphological behaviors. The results lead to a picture of gelation as a continuation of the glass transition into the two-phase region, or equivalently, as an incomplete phase separation arrested by the onset of the glass transition.

It is well known that HPAs (High Power Amplifiers) are inherently nonlinear devices and many researches have focused on the predistortion for memoryless HPAs. However, memory effects of HPAs can no longer be ignored when communication systems have wider bandwidth. Memoryless predistortion techniques proposed previously seldom have satisfactory effectiveness for typical wideband applications such as OFDM (Orthogonal Frequency Division Multiplexing) systems. In this paper, an improved adaptive predistortion method called 2D LUT (2-dimension look-up table) with different accuracy levels is presented to linearize HPAs with memory effects. Simulation and experimental results show that 2D LUT implements excellent performance in mitigating the signal deterioration caused by memory effects, both rectifies the signal constellation distortion and suppresses the spectrum emission. Large scale matrix computation is also avoidable in these adaptive algorithms, which makes them feasible when a real-time system is necessary. Index Terms--HPA, memory effects, nonlinearity, OFDM, predistortion.

A general method for the mimicry of one face of an alpha-helix based on a terphenyl scaffold that spatially projects functionality in a manner similar to that of two turns of an alpha-helix is described. Terphenyl derivative exhibited binding affinity in the nanomolar range and terphenyl serves as a general scaffold to mimic alpha-helical segments with good selectivity in recognition of different helix-binding proteins.

The absorption spectra and the Hyper-Rayleigh scattering (HRS) signals of a highly monodisperse 10.5-nm diameter silver colloids are measured with the addition of KNO(sub 3) and pyridine. Strongly enhanced HRS signals are observed by 15x and 6x respectively.

The alternating current photoconductivity (ac-PC) of TiGaS2 layered single crystals and the spectral distribution of the photocurrent is studied at different values of light intensity, applied voltage, and temperature. A continuous distribution of traps in the energy gap is presented by the values of the photoconductivity response time, which are reported from the light intensity dependence of ac-PC.

The conformation of poly(ethylene glycol) chains with molecular mass 5000 (PEG5000) grafted onto phospholipid monolayers at the air/water interface is highlighted. Conformational changes in PEG5000 chains grafted onto the phospholipid monolayer are therefore described as a transition from a highly hydrated pancake to a poorly hydrated brush conformation.

Based on the distinct element method, a numerical procedure is presented for simulation of creep behavior of jointed rock slopes due to excavation unloading. The Kelvin model is used to simulate viscous deformation of joints. A numerical scheme is introduced to create incremental contact forces, which are equivalent to producing creep deformation of a rock-joint system. The corresponding displacement of discrete blocks due to creep deformation of contact joints can be calculated by equilibrium iteration. Comparisons of results between the numerical model and theoretical solutions of a benchmark example show that the presented model has excellent accuracy for analysis of creep deformation of rock-joint structures. As an application of the model, residual deformations of the high rock slopes of the Three Gorges shiplock due to excavation unloading and creep behavior are investigated. By simulating the actual excavation process, the deformation history of a shiplock slope is studied. Good agreement has been achieved between numerical prediction and field measurements. It demonstrates the effectiveness of the presented model in analysis of the creep deformation due to excavation unloading of high rock slopes.

Double-wall carbon nanotubes (DWCNTs) are synthesized by pyrolyzing C2H2 on the sulphur- promoted floating iron catalyst. In the floating catalyst system, tunable growth of DWCNTs with different diameters was achieved.

The fundamental and overtone absolute intensities of the perpendicular band of isolated CH chromophore in chloroform (CHCl3), bromoform (CHBr3), and iodoform (CHI3) are calculated. The results show that the calculations agree with experimental data within a factor of 2 for most of the observed bands, and the discrepancies between the calculation and the observation are most probably to arise from the DFT calculations.

A vibrational basis representation example and a discrete variable representation example demonstrate that it is possible to use the Lanczos method and exclude direct product basis functions. This is achieved by restricting the basis function indices while maintaining the favorable n(super f+1) scaling relation for the cost of direct product basis matrix-vector products.

Automatic 3D object model construction is important in applications ranging from manufacturing to entertainment, since CAD models of existing objects may be either unavailable or unusable. We describe a prototype system for automatically registering and integrating multiple views of objects from range data. The results can then be used to construct geometric models of the objects. New techniques for handling key problems such as robust estimation of transformations relating multiple views and seamless integration of registered data to form an unbroken surface have been proposed and implemented in the system. Experimental results on real surface data acquired using a digital interferometric sensor as well as a laser range scanner demonstrate the good performance of our system. Index Terms - Automatic 3D object modeling, free-form objects, registration, view integration, range images, digital interferometry.

The ability of endothelin (ET)-1 to constrict the hepatic vascular resistance distribution and ETA and ETB receptors in isolated rabbit livers perfused via the portal vein was investigated. Twenty-nine rabbits were used as experimental models to determine the effects of ET-1 on liver hemodynamics, weight and bile flow as well as the effects of ET receptor antagonists on hepatic vasoconstriction response caused by ET-1. Results showed that ETA and ETB receptors indeed mediated ET-1-induced hepatic constriction in rabbit livers.

A new distributed principle of bus protection is presented. The protection system description, its design features, hardware structure, data communication network construction and protection algorithms are discussed. Performance analysis and preliminary experiments show its distinguishing advantages over the traditional centralized principle. Keywords: Bus Protection, Data Communication, Digital Relaying

R-Ras enhances the activity of a cell death pathway in growth factor deprived cells via a Bcl-2 suppressible mechanism. Examination of Bcl-2 mechanism shows its ineffectiveness in the R-Ras GTPase activity and in the protein exchange for R-Ras in vitro. There is correlation between faster rate of cell death and higher levels of R-Ras upon withdrawal of interleukin-3 from protein cultures.

The simple-assembled two dimensional random networks composed of isolated SWNTs are obtained by a simple floating catalyst CVD method. The conclusion states that the deposited SWNTs constituting the networks are isolated rather than in bundles and this result should be help for improving the preparation technique and exploring the formation mechanism of SWNTs.

A general and efficient method to preparate the optically active [Z.sub.1][Z.sub.2]P(O)Cl from the easily prepared optically active H-phosphinates and H-phosphine oxides is described. Optically active [Z.sub.1][Z.sub.2]P(O)Cl is found to react easily with a variety of nucleophiles to produce other chiral organophosphorus acid derivatives with inversion of configuration at phosphorus.

Several studies are conducted to explain the different light emission properties of the planar source present in the different multilayer structures with different photonic crystal patterns. The working of the different optoelectronic devices based on these patterns is also analyzed.

Modified Sharpless asymmetric epoxidation is used for achieving sequential coupling reactions, and a divergent strategy, the protection-free syntheses of two main pheromonal components found in the fall webworm moth, Hyphantria cunea, and other species. The overall yields and the ee values of the final products are discussed.

The reaction of H-phosphinates and secondary phosphine oxides with amines and alcohols has stereospecifically produced the corresponding coupling products with inversion of configuration at the phosphorus center under the Atherton-Todd reaction conditions. The studies have provided an efficient method for preparing a variety of optically active organophosphorus acid derivatives from chiral H-phosphinates and secondary phosphine oxides.

An advanced three-dimensional electrothemal-coupled simulation model basing on finite-element method numerical simulation is developed for analyzing the electrical and thermal properties of chip-level high-power GaN-based light-emitting diodes (LEDs). A thermal effective bump configuration is described and the results have shown that a lower average temperature and uniform heat distribution are obtained in the chips.

A systematic shape variation of zinc blende CdSe nanocrystals is demonstrated in a modified organometallic approach, in which distinct shapes of cube-shaped, sphere-shaped, tetrahedron-shaped and branched CdSe nanocrystals with high yield and good uniformity are obtained. The wide variation of shapes has provided important information about the growth of CdSe nanocrystals and it has helped in the shape-controlled synthesis of other nanocrystals that are bound with uniform crystal planes.

Monte Carlo method is used for studying the characteristics of gallium nitride (GaN). Impact ionization is treated as an additional scattering mechanism and the results of velocity overshoot and impact ionization rate of both carriers are analyzed.

The aerobic oxidative coupling of terminal alkynes with H-phosphonates to obtain alkynylphosphonates is presented. The coupling reaction is carried out in presence of copper as catalyst to increase the yield of the alkynylphosphonates.

The [Ce.sup.3+] and [Dy.sup.3+] codoped oxyfluoride glasses and glass ceramics containing La[F.sub.3] nanocrystals are prepared in the reducing atmosphere. The glasses and glass ceramics have emitted bright light by adjusting the concentration ratio of [Ce.sup.3+] to [Dy.sup.3+].

A phase sensitive time resolved z-scan method is employed to study the relationship between Kerr effect and terahertz related Kerr-like nonlinear effect observed in one ZnTe crystal used as terahertz emitter and detector. The removal of nonlinear two-photon absorption of the probe beam showed that the phase change in probe beam is due to Kerr effect and terahertz related Kerr-like effect.